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Home Gardener’s Guide

Horticulture Tips for August


Oklahoma Cooperative Extension Service

Division of Agricultural Sciences and Natural Resources

Oklahoma State University



David Hillock


  • August is a good month to start your fall vegetable garden.  Bush beans, cucumbers, and summer squash can be replanted for another crop.  Beets, broccoli, carrots, potatoes, lettuce, and other cool-season crops can also be planted at this time. (HLA-6009)
  • Soak vegetable seed overnight prior to planting.  Once planted, cover them with compost to avoid soil crusting.  Mulch to keep planting bed moist and provide shade during initial establishment.  Monitor and control insect pests that prevent a good start of plants in your fall garden.

Fruit and Nut

  • Continue protective insect applications on the fruit orchard.  A good spray schedule is often abandoned too early.  Follow directions on last application prior to harvest. (EPP-7319)


  • Towards the end of the month, divide and replant spring-blooming perennials like iris, peonies, and daylilies if needed.


  • Water compost during extremely dry periods so that it remains active.  Turn the pile to generate heat throughout for proper sterilization.
  • Always follow directions on both synthetic and natural pesticide products.
  • Watch for high populations of caterpillars, aphids, spider mites, thrips, scales and other insects on plant material in the garden and landscape and treat as needed. (EPP-7306)
  • Water all plants thoroughly unless rainfall has been adequate.  It is better to water more in depth, less often and early in the morning.

Trees and Shrubs

  • Discontinue deadheading roses by mid-August to help initiate winter hardiness.
  • Watch for secondgeneration of fall webworm in late August/early September.  Remove webs that enclose branches and destroy; or spray with good penetration with an appropriate insecticide.

Lawn and Turf

  • Grassy winter weeds like Poa annua, better known as annual bluegrass, can be prevented with a preemergence herbicide application in late August. Water in the product after application. (HLA-6420)
  • Areas of turf with large brown spots should be checked for high numbers of grubs.  Mid-to-late August is the best time to control heavy white grub infestations in the lawn. Apply appropriate insecticide if white grubs are a problem. Water product into soil. (EPP-7306)
  • Tall fescue should be mowed at 3 inches during the hot summer and up to 3½ inches if it grows under heavier shade. (HLA-6420)
  • For areas being converted to tall fescue this fall, begin spraying out bermudagrass with a product containing glyphosate in early August. (HLA-6419)
  • Irrigated warm-season lawns can be fertilized once again; apply 0.5 lb N/1,000 sq ft in early to mid-August.
  • Brown patch of cool-season grasses can be a problem. (HLA-6420)


employee garden

Pecan Crop Load

Becky Carroll

Although pecan crops may be short in some areas due to late freezes and drought conditions, other pecan growers with improved varieties should be checking crop loads to determine if they need to mechanically thin their pecans. On large fruited pecans such as Mohawk and Maramec, only about 50% of the terminals should have clusters. On smaller varieties, 60-70% of terminals can be fruiting. If more terminals are fruiting than recommended, the pecans should be thinned.

Crop load thinning is usually done the first week or two of August or more specifically when the pecans are in the water stage when the ovule has expanded between 50-100%. Just as peaches and apples are thinned, pecans will greatly benefit from crop load management. Thinning the fruit will increase fruit quality, help reduce alternate bearing, as well as reduce the possibility for and severity of winter freeze damage.

Pecans can be mechanically thinned with a conventional shaker fitted with donut pads. Be sure to keep the underneath of the flaps on the donut pads greased to help limit barking the trees. Fact Sheet HLA-6251 Pecan Crop Load Management details the procedure.



Becky Carroll 

Weevil traps should be placed in the orchard at this time.  The Circle trap is the preferred trap for monitoring weevil emergence.  Fact Sheet EPP-7190 Monitoring Adult Weevil Populations in Pecan and Fruit Trees in Oklahoma explains how to construct and when and where to place the traps. With the recent rains, weevil will be emerging and feeding on nuts until the dough stage when they start laying eggs in the pecans.  Have a plan for weevil control and be ready to spray to prevent losses. When pecan crops are small, weevil feeding will add to the reduction in the crop. When weevils feed on the nut early, the nuts usually fall to the ground. Growers will need to assess when they should start protecting their crop. Each orchard will be different. With heavy crops, weevil feeding may not be too detrimental during the water stage, but once the fruit begins to change stages, growers will want to try to eliminate the egg laying phase that will reduce quality and prices.


Save Water this Summer!

David Hillock

While many of us have been blessed with rainfall this summer when we normally don’t receive it, water conservation should still be on our minds. WaterSense® is a U.S. EPA partnership program promoting water conservation and has created this infographic on water waste and how we can reduce some of the common problems.



Performance of Determinant Tomato Varieties for Hot Weather Production

Danielle Williams, Lynn Brandenberger, Brian Kahn

Tomatoes are a “must-have” for Oklahoma consumers that want locally-grown fresh produce.  Tomatoes are not only popular, but they are also a high maintenance crop.  Oklahomans have grown tomatoes as long as they have gardened and each year battle hot, dry summers and arduously tend to this high maintenance vegetable crop.  Great detail goes into managing this crop including planting, watering, and managing nutrient levels, but nothing can be done to lower Oklahoma summer temperatures.  Utilizing methods such as mulch, drip irrigation, shading, and plasticulture help growers manage soil temperature and moisture levels, but it still is not enough in intensely hot years such as 2011 and 2012.  Growers have difficulty growing tomatoes in Oklahoma summers when temperatures in June and July, and many times August, exceed the optimum range to encourage fruit set.  Farmers continually request assistance in growing tomatoes in such conditions; varieties that exhibit superior heat capabilities may make this possible.

Not all flowers result in fruit. Daytime temperatures between 70-84oF and nighttime temperatures 65-68oF are the optimum temperature ranges for pollination.  Poor fruit set occurs above 90oF; tomato plants will flower, but the pollen and stigma dry out quickly preventing pollination or fruit set. During June-September 2011 there were 99 days above 90oF in Stillwater, Oklahoma, and 68 days in 2012.  Growing practices such as plasticulture, organic mulches and shading may help maintain plants until fall when temperatures drop to the optimal range for fruit set, but this does not help a farmer during the summer market season.  To address this problem selected tomato varieties with potential heat-set capabilities were grown in replicated trials at two locations in Oklahoma in 2012, and four locations in 2013.

Results and further details are available in the 2012 and 2013 Vegetable Trial Reports (MP-164).  After analyzation of data and growers’ feedback was attained from 2012, selections of varieties to be grown in 2013 expanded trials were made.  Twelve varieties were again chosen and grown in four locations in 2013.  All locations utilized plasticulture except Tulsa, which used permaculture.

Temperatures and growing conditions varied between the two seasons: 2012 was much hotter while late frosts, hail storms, and a warm fall were experienced in 2013. Despite lower temperatures and higher rainfall than 2012 there were common results for several of the varieties.  Solar Fire, Bella Rosa, Tribeca and Tribute stood out in top marketable yields.  Solar Fire produced in the top three at all locations in 2013 and one location in 2012.  Bella Rosa and Tribeca were both in the top five producing varieties at three locations in 2013 and one location in 2012.  Tribute was in the top five at two locations in 2013 and also in 2012.


2014 All-America Selection Winners

David Hillock

All-America Selections is an independent, non-profit organization that tests new varieties then introduces only the best garden performers as AAS Winners.

The AAS Winners offer gardeners reliable new varieties that have proven their superior garden performance in Trial Grounds across North America, thus, their tagline of “Tested Nationally and Proven Locally®”. When you purchase an AAS Winner, you know that it has been put through its paces by an independent, neutral trialing organization and has been judged by experts in their field. The AAS Winner label is like a stamp of approval.

Here are a few of this year’s winners. For more information about these and other winners, go to



Angelonia Serenita™ Pink F1
2014 AAS Flower Award Winner

Elegant yet tough plants bring long-lasting color with very little maintenance. These look beautiful in mixed combos on the patio or create a soothing sea of soft color in the landscape. Heat-tolerant plants.  Deer and rabbit resistant. Grows 12-14″ tall by 12-14″ wide.


Gaura Sparkle White
2014 AAS Bedding Plant Award Winner

Sparkle White gaura will bring a touch of airy elegance to the garden with its long slender stems sporting a large number of dainty white flowers tinged with a pink blush. This beauty is perfect mass planted in sun-drenched landscape beds, in groupings with other perennials or in larger containers. Home gardeners will appreciate that this season-long bloomer also has excellent heat tolerance and a more uniform flowering habit than other seed gauras. Sparkle White is also a recipient of Europe’s FleuroSelect Gold Medal award for garden performance.

Petunia African Sunset F1
2014 AAS Bedding Plant Award Winner

African Sunset wowed the judges with an attractive, “designer color” in shades of orange flowers that proved itself against other similarly colored petunias currently available. Gardeners are always looking for a petunia that grows evenly and uniformly in the garden while producing a prolific number of blooms all season-long and this beauty certainly fills that need. Many of our judges want this in plantings for their alma mater so if your school colors include orange, this one is for you! Mounded spreading plants are 12 inches tall spread up to 32 inches.
New for 2014 are regional winners. Below are some of the regional vegetable winners.



Cucumber Saladmore Bush F1
2014 AAS Vegetable Award Winner

Award Type: Regional (Southeast)

Matures in 55 days from sowing.  This semi bush vine sets sweet crisp cucumbers as long as you keep them picked. Good garden performance due to the multiple disease resistances. Has dual use, pick small for processing as pickles and harvest larger for fresh slices or spears.

Pumpkin Cinderella’s Carriage F1
2014 AAS Vegetable Award Winner

Award Type: Regional (Southeast, Great Lakes, Mountain/Southwest)

Cinderella’s Carriage is a dream come true for any princess-loving child who wants to grow their own fairy tale type pumpkin. This bright reddish-orange pumpkin is the first hybrid Cinderella-type pumpkin on the market which results in a higher yield as well as Powdery Mildew resistance in the garden. Robust and vigorous vines produce large fruits ranging from 25-35 pounds, creating a whole grouping of carriages for all the princesses in your family

Magical pink-red colored fruit shaped like the pumpkin carriage from the fairy tale Cinderella. Some lucky gardeners could also experience a pale blue pumpkin. Large trailing vine sets up to 5-7 fruit per plant. Well suited for fall decorations and baking. Flesh is yellow, sweet and has a nutty flavor.


Radish Rivoli
2014 AAS Vegetable Award Winner  

Award Type: Regional (Southeast, Heartland, West/Northwest)

Upright healthy leaves with fruit that is an even-colored bright red. Uniform roots are very round and about 1½” inches in diameter. Interior texture is smooth and dense with bright white color, even when roots get large. Exceptional quality and taste when picked young, but still tasty if allowed to sit in the garden longer, giving gardener an extended harvest opportunity.